Key for interpreting lengths in a plot

Key for interpreting lengths in a plot

Usage

lengthKey(x,y,tickpos,scale)

Arguments

x,y

The position of the left end of the key in user units.

tickpos

The labels that will appear above the key.

scale

A value that will scale the length of the key.

Value

nil

Details

lengthKey displays a line with tick marks and the values in tickpos above those tickmarks. It is useful when line segments on a plot represent numeric values. Note that if the plot does not have a 1:1 aspect ratio, a length key is usually misleading.

Author

Jim Lemon

See also

segments, arrows

Examples

 # manufacture a matrix of orientations in radians
 o<-matrix(rep(pi*seq(0.1,0.8,by=0.1),7),ncol=8,byrow=TRUE)
 m<-matrix(rnorm(56)+4,ncol=8,byrow=TRUE)
 # get an empty plot of approximately 1:1 aspect ratio
 plot(0,xlim=c(0.7,8.3),ylim=c(0.7,7.3),type="n")
 vectorField(o,m,vecspec="rad")
 # the scaling usually has to be worked out by trial and error
 lengthKey(0.3,-0.5,c(0,5,10),0.24)